Desmosomes are essential cell-cell adhesion structures that provide mechanical integrity to tissues. Disruption of desmosomes leads to a range of diseases in man including skin fragility and blistering disorders as well as cardiomyopathies. The textbook view of desmosomes is that they are rather passive structures that simply bind to the intermediate filament cytoskeleton. We are now beginning to appreciate that desmosomes are both more dynamic and have more functions than previously thought. For example, we have shown that desmosomes control microtubule organization in the epidermis and cultured keratinocytes. In this application, we focus on how desmosomes control the organization of cytoskeletal networks. Our central hypothesis is that the desmosome actively organizes both intermediate filaments and microtubules through recruitment of a protein complex that is usually found at the centrosome. Some of the novel desmosomal proteins in this complex, including Lis1 and NDEL1, are known to control microtubule and intermediate filament organization in other tissues. By understanding both how these proteins are recruited to desmosomes and their functional role there, we will greatly expand our knowledge of how desmosomes control the cytoskeleton. This will allow us to specifically disrupt microtubule organization in differentiated epidermis, and to determine the physiological function of cortical microtubules in these cells. To accomplish this, we will generate and characterize mouse models in which centrosomal proteins are not recruited to desmosomes. This will directly test the physiological role of this novel desmosomal function. Second, we will determine how loss of Lis1 in the epidermis leads to defects in epidermal integrity, desmosome architecture, and microtubule organization. Third, we will determine the role of the novel keratin-binding protein, NDEL1, in controlling keratin filament organization downstream of the desmosome. This work will lead to a mechanistic understanding of how desmosomes reorganize the underlying cytoskeleton and to a greater understanding of why desmosome disruption results in such a diversity of pathological phenotypes. PUBLIC HEALTH RELEVANCE: Desmosomes are cell-cell adhesion structures that provide mechanical integrity to cells by linking to the underlying cytoskeleton network. Disruption of desmosomes causes epidermal fragility, skin blistering, and cardiomyopathies. We will characterize novel mechanisms that desmosomes use to reorganize the cytoskeleton. This will allow an understanding of how desmosome disruption results in such a diversity of pathological phenotypes.